laytton



(No Model.)

' I C. F., A. W. AT, A. L. LAWTON.

l PROCESS 0F MANUFACTURING SALT. No. 475,576.

Patented May 24, 1892.

UNITED STATES ArENr ".GEFICE.

vcnnRLEs R Lawton, ARTHUR w. Lnwfox, AND ALnERrL; i.nivjrofgor ROCHESTER, NEW YORK.

PROCESS OF MANUFACTURING SALT SPECIFICATION forming part of Letters Patent No. 475,576, dated May 24, 1892'. Y

y riginal application led February 9, 1891, Serial No. S80/78d. Divided andthis application filed January 2, 1892,. SeralfNo 416,827. (No specimens.)

' T0 @ZZ whom it 77mg/ concern: Be it known lthat we, CHARLES F. LAWTON,

ARTHUR W. LAwroN, and ALBERT L. Law- TON, citizens of the United States, residing at Rochester, inthe county of Monroe and State of New York, have` invented certain new and use ful Improvements in the Process of Manufacturing Salt, of which the following is a specification, this specification being a divisio ion of an application, Serial No. 380,783, tiled by us February 9, 1891.

Our invention relates to the. manufactu re of salt, (chloride of sodimm) and has reference more particularly to a process for the purifir cation and whitening thereof.

"Briefly stated the invention consists in the process o'f providing a furnace, chamber, or other suitable receptacle with a protecting face or lining of basic infusible material,

zo placing salt therein, and subjecting the salt to a fusing heat, advisably adding to the salt, before or after fusion, alkaline material.

One form of apparatus for carrying out the invention is, for the purposes of illustration,

2 5 shown in the drawing, which isa vertical sectional view of a furnace. This form gives good results; but we wish it understood that we do not limit ourselves to the construction shown 0r to any particular form, as many 3o other forms of melting-furnaces may be substituted with equally good results.

The apparatus here shown consists of a fireplace A, a receptacle B for the melted or fused salt, two fines or passages C and D, the former 3 5 directly over the latter and inclined, as shown,

and a series of steps i t' t' between the two f fines. Between these steps are openings through which the hot gases from the fire' pass and come in contact with the salt resting 4o upon the steps, the gases also passing around the lower end of the hopper G, and finally up into the iine or chimney F. The steps i inl oline downward toward the furnace, so as to cause the fused ork melted salt to run down .45 into the'receptacle B, where the impurities and the purified salt aresseparatelydrawn 0E 5o into suitable receptacles or molds.

H is a tube through which a rodis occasionally thrust to see when the salt in ythe receptacleis deep enough for drawing oi.l At the upper end of the flue D is placed a tvalve or damper E, which when closed causes the hea-t to pass through the spaces between the steps. but when opened, (as for instance in'startng a iire,) allows the products of combustion to pass directly to the chimney. Tith the valve 6o closed salt is `fed through the hopperonto the uppermost step, and as the body of salt works its way down the flue C from step to step it is subjected to the action of heat, (varying from 900O to 1,4300 Fahrenheit,) the degree of heat increasing as the salt continues its travel, so that by the time the salt reaches `thelowerniost step it will run therefrom into thereceptacle B in a fusedl or molten condition. The crucible or receptacle B, being located in 7o proximity to the fire, is kept at a higl1-teinperature to prevent the cooling of the fused salt therein.

The process just described is that which is employed in reducing comparatively coarse mined or rock salt; but where the salt to be melted is in the form of a powder-thedoorof the ash-pit should be closed and au artificial but gentle air-blast injected underthe grate, so as to force the hot gases from the lire 8o through the powdered salt on the steps.

An alkali or alkaline material may be mixed with the salt prior to its fusion .or subsequently thereto, and may also be applied in a hydrated or anhydrous state; or the. al'kalies 85 may, before or at the time of using, be combined with weak acids, such as silica or earbonie acid. Some of the alkalies and their compounds that may be used alone or two or more together are lime, magnesia, ,strontia, 9o soda, and potash, their silicates, carbonates, and hydrates, ,or such substances in an anhydrous caustic state. In practice we have found caustic lime, eitherhydrated or anhydrous, as good as anything else, andfind lthat the quantity required is from one-half of lone i per cent. to two percent. of lime to. ninety- 'nine and one-half yto ,ninetylfeightper cent. of

salt.' These proportions may, however, be varied-somewhat. V I

In using thesilicate or the. carbonate of lime more time is required to produce the nesia, nla'gnesia carbonate, soda, and potash also work Well in purifying and whitening 1s alt, but' their cost far exceeds that of the ime.

In using the alkali or materials of an alka- `line nature they may be sprinkled over or distributed through the salt before itis fused; or the powdered alkali may be thrown onto or stirred into the salt after fusion. After thesalt containing the alkali isfused and Vrun into a large infusible crucible or receptacle we allow it to stand from five to thirty minutes to give time for the alkali to act on the salt.Y We then draw ed the dregs or impur-ities which had previously settled to the -Ibottom and then draw olf the purifed salt from the bottom of the receptacle containing it. When a smaller percentage of alkali is used, it is necessary for the fused salt to stand a longer time to settle the impurities and to give the desired effect.

Instead of sprinkling the salt with a powdered alkali or mixing the alkali with the prev iouslyffused salt the alkali may be worked into the basicmaterial or lining of the furnace and crucible in larger proportion than we would otherwise use, and this extra-strongly basic lining and material 'will of itself whiteu the salt, b utit takes more time than when the powdered alkali is mixed with the salt direct. Whenthe proportion of lime or magnesia in this lining mortar is very large, the composin tion will not readily fuse by contact with the melted salt, and at the same time will cohere sufficiently not to break down.

To save fuel, we prefer to conduct the hot gases from the lire into direct contact with 'the salt to be melted, such dustor soot as gets into the .melted salt settling with the other impurities in the bottom of the fused-salt crucible or receptacle. y

A furnace which will produce carbonio-ox- ,idebr carbon-monoxide gas and hydrogenV can' be substituted for the `furnace shown; the heat escapingfrom the furnace after pass-` ing through and over the salt being recovered thoroughly mixing it with the melted salt or coating the molds into which it is poured.

The formation of fusible silicates is prevented by constructing an those parts of the furnace that come in contact with the salt of a strongly basic infusible composition, made of a mixture of four parts of lime to one part of good clay, as free from iron as possible.. By the use of this mixture the decomposition of the salt andthe formation of soda' silicate is avoided by reason of the superior attrae tion of the lime for the little silica in the clay with which it is mixed. The fused salt not coming in contact with any silica. with which it can react, remains unchanged so far as the i formation of silicate of soda is concerned,all of which becomes a matter of the utmost importan ce when it is considered that no other substance (except, perhaps, some virulent poison) could be more injurious to the s'alt.'

When the quantity of soda silicate isv so small that it will form a heavy insoluble precipitate with the impurities in the salt, no injury will result because of the elimination of the silicate through such precipitation.

The term lining is used throughoutithis specification as meaning and includingr a pro- -tecting face or surface for the exposed parts of the apparatus, whether such protection be extended into or throughout the thickness or body of the chamber, furnace, or receptacle,

or merely applied as a surface coating.

In the construction of furnaces the lining is commonly made. in the form of bricks, and such a lining-that is, aV lining of bricks of basic infusible material is comprehended in the present invention. XVe are aware that within recent years a basic infusible lining has been employed in a Bessemer smelting-,furnace because of lthe chemical affinity lwhich the basic lining has for the phosphorus in the iron under treatment, and to this we make no claim.

Our invention resides in great part in the discovery that the chemical action of salt vapors upon a furnace or vessel may be Aprevented from taking place by the employment of a furnace, vessel, or chamber formed of or lined with a basic infusible substance, which, by reason of its inert qualities, not only pre` serves the furnace from destruction, but also precludes the formation of a fusible .silicate of soda, the presenceof which would render the salt practically useless and unmarketable.

By our process we produce a table-salt chemicallypure, andconsequently non-hygroscopic, and this,^tco, at a cost less than byv the evaporationprocess now universally used.

This application is a division of an appli- ICJO cation tiled by us February 9,1891, Serial N o.

the action oflheat andof a'niaterial of an aiexposed surfaces-is embraced in our afore-A said application.

The process described in our aforesaid prior application, Serial No. 380,223, maybe einployed in connection with or carried out in a furnace or vessel having the basic infusible lining of the present case, and it is for this reason that the cnt-ire operation or the different modes of operation are set forth in the present application. The claims of this case are, however, restricted to the process as carried out in connection with the basic infusible material to protect the exposed parts of the apparatus, as above explained ln Vpractice it is found advantageous to perform 'the operation purifying salt. as a continuous process, the fire in such case being' maintained for-an indefinite period, and additional charges of saltbeing placed in the reducing vessel or chamber to repiace the fused or purified salt drawn odi.

Thev basic infusibie lining once applied will last for a long period, and 'may iastindefinitely. Hence it is to be understood. that the step in the process or the act which consists in lining the furnace with a basic infnsible material will .not requireA to be repeated with each batch of salt or with each firing, but only when,if ever, the lining deteriorates and becomes incapable of resisting the action of the salt vapors. l

Having thus described our invention, what we claim is l. The hereindescribed method of purifying salt, (chleride'ofsodinm,) which consists in first lining a receptacle with a basic 1ni'usibie material, such as described, next pia@ ing salt ther in', and finally fusing the salt in said receptacle, whereby the salt is purified and the formation of silicates is pre wanted.l

2. The method o purifying` salt, (chloride of sodinnn) which consists in1 the ioiicwing steps, viz: ining a receptacle with basic infnsible material, linie and cia-y, which will, byreason ci its inert chemical qualities, prevent the formation of soda .silicate and the destruction of the rcceptacle,piacing salt L' in said receptacle, fusing-the salt therein, and adding to the salt before or after fusion an alkaline material.

In Witness whereof We hereunto set our hands in the presence of two witnesses.

CHARLES F. LAVTON. ARTHUR YV. LANTON. ALBERT L. LAWTON.

Nitnesaes to the signature ot' A, XV. Lauvton:

M. H. 'Sn-ieee, A. F. Pntnnirs. Witnesses to the signatures ci (1F. and A. L. Lawton:

Hormon A. DODGE, WALTER S. DODGE. 

